Learn more about errors and/or corrections related to 3DEP Digital Elevation Models.
FTP Access (July 2021)
The National Map (TNM) stores lidar for download on an FTP site. Google Chrome, Microsoft Edge, and Firefox browsers dropped support for FTP. For downloading lidar through a web browser, the temporary solution was use another web browser or use other options such as uGET or FTP client software.
Fix: USGS has replaced the FTP server with an HTTPS server. Data can be downloaded from the HTTPs Server.
Elevation Index Transition
We are in the process of transitioning to a new enhanced 3DEP Elevation Index service, so not all of the latest lidar project areas are visible on the old index currently seen in our viewers. Lidar projects published since May 7, 2020 may be viewed as a web map. This data can be accessed in the Lidar Explorer and the National Map Downloader through search, even though it is currently not visible on the index. We plan to have the new 3DEP Elevation Index available in December 2020. In the meantime, this map can be used in conjunction (by having this map open in another window) along with our download applications to help find the latest lidar data.
3DEP Data Issue Announcement Regarding XML Metadata (February 2020)
Issue: An error in the coordinate reference system (CRS) tags was discovered in the XML metadata for the DEM Source, lidar point cloud (LPC), and 1m layers. The CRS tags in all of these xml files showed data in UTM Zone 30, regardless of the actual coordinate reference system in the file. The error was caused by how a tag in geotiff files was being read and converted by the USGS production software. All data published from April 2019 until the end of January 2020 contained this issue.
This error did not impact the positional accuracy of the data, and all metadata provided by the lidar acquisition contractor was correct. To find the contractor metadata, go the Lidar Explorer. Click on the lidar project name, and click on the “From FTP” link at the top of the window. The contractor metadata is in the zip file located in the metadata folder inside each project folder.
Fix: As of April 2020, all of the affected XML metadata has been corrected and republished.
3DEP Data Issue Announcement Regarding 1-meter resolution DEMs (July 2018)
Issue: A linear “banding” or “striping” artifact was discovered in some of the 1-m Digital Elevation Models (DEMs) available on The National Map. The artifact was caused when an update to the code in the 3DEP elevation production software unintentionally changed the resampling method used during the reprojection of the source DEMs to the 1-m standard UTM coordinate reference system. The artifacts are most noticeable in areas with a slope of 10 degrees or greater, and the artifacts could degrade the vertical accuracy of the DEMs. The 3DEP 1-m DEMs produced from the beginning of January 2017 until the end of May 2018 are affected.
Fix: A fix was identified and as of August 2019 all of the affected DEMs have been reprocessed. The corrected 1-m DEMs were published as part of The National Map.
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